Yes but each SAQP is an ArFi mandrel mask and an ArFi cut mask and that happens multiple times. By my count Samsungs 16nm 2D NAND has 18 ArFi masks and their 48L 3D NAND has only 6 ArFi layers.
Stair step is multiple masks because they can only shrink the resist so many times before they have to remask but it is I-line or KrF masks and they are pretty cheap.
In the array formation the layers are deposited and channels are one mask and etch down through the whole stack, word line trench is also one mask and etch down through the whole stack. I don't see a whole lot of etches for 3D NAND although some are really slow.
15nm NAND has more than 1 SAQP step and SAQP requires multiple ArFi exposures that are really expensive.
64 etches sounds high to me but I would have to go count them to be sure, there are multiple step etches, for example the stair step is etch, shrink resist etch multiple times but it is done on one tool in a sequence.
I have detailed flows for both 15nm 2D NAND and 32L 3D NAND that I base my analysis on. When I compare 32L 3D to 15nm 2D from Micron my cost savings for 3D comes out to 20% and that is exactly what they have said it is publically.